The present invention is generally in the field of implantable microchip devices and methods for use thereof, particularly in ophthalmic and other medical applications.
The relatively small size, rounded shape, and location of the eye have made the development of new methods and devices for drug delivery to the eye difficult. The most common method of drug delivery to the eye is by liquid eye drops. This method of drug delivery is limited to those drugs that can diffuse through the eye tissue (i.e. typically low molecular weight drugs) and those drugs that can be formulated as a liquid or gel.
Alternative delivery methods include the implantation of drug delivery devices inside of the eye. For example, U.S. Pat. No. 6,063,116 to Kelleher discloses an intraocular polymeric implant for sustained release of a cell proliferation-modulating agent. As another example, Ambati, et al, “Transscleral Delivery of Antibodies to the Posterior Segment” Investigative Ophthalm. & Visual Sci., 40(4): 457-B417 (Mar. 15, 1999) discloses implanting osmotic pumps containing FITC-IgG on the scleral surface or beneath a lamellar scleral flap for targeted delivery to the choroid and retina.
These implants may allow larger molecular weight drugs to be delivered (depending on the presence of diffusion limitations based on the depth of the target tissue layer), but they typically only have the ability to passively release a single drug.
PCT WO 00/40089 discloses a method for delivering a therapeutic or diagnostic agent to the retina and choroid by contacting the sclera with the agent and using an implant device for enhancing transport of the agent through the sclera. The reference mentions that the implant can be a microchip comprising reservoirs containing the desired agent. It would be advantageous to develop new and improved systems using microchip devices, as described in U.S. Pat. Nos. 5,797,898, 6,123,861, PCT WO 01/64344, PCT WO 01/35928, and PCT WO 01/12157, for the controlled delivery of drugs and the controlled exposure of sensors in ophthalmic and other medical applications wherein implantation presents challenges such as described above for the eye. It also would be desirable to provide devices and methods of use thereof for delivery and sensing at locations in patients where implantation is desirable in small spaces, particularly those involving curved or rounded tissue surfaces.